Autobalance/ Servo Driven coil

[Sean_Goddard]

Has anyone made a coil which "autobalances"?

I am under the impression that one of the biggest problems which affect sensitivity of a VLF is Rx saturation due to the mineral matrix in the ground setting up a "standing" signal thus masking the tiny target signals. I want to know if anyone has made a ground balance system which nulls the COIL to the effect of the mineral matrix thus (theoretically) increasing the amount of gain which can be used in the Rx thus giving better sensitivity?

[AK48]

https://patentimages.storage.googlea.../US8120456.pdf

[Skippy]

The XP Deus does some sort of auto-calibration at power-on, which requires the operator to hold the coil clear of the ground during this process. I did wonder if having the coil fixed at a typical sweep height ( ie. zero movement, like sitting on a bit of wood ) would cause it to calibrate out the ground signal as well as the air signal.
The auto-cal is likely needed on the Deus because it's selectable frequency means the coil isn't that well balanced, not at all the freqs, anyway.

This is really only relevant to folks with very bad ground, like the red Australian stuff, or what's found in Tennessee, USA. For most locations, including us here in the UK, the air signal dwarfs the typical ground signal.

[Carl-NC]

Coils are factory nulled to air, so the air signal should always be minuscule compared to any ground signal. Most ground is not so severe that it overloads the RX and it is normally removed by the motion filtering. But it can limit how much gain you can run in the RX. At White's I did some work on a self-nulling coil. Stage 1 was to make a coil that could be electronically nulled to air, replacing the tedious factory tweaking with a simple one-time auto method. Stage 2 was to make it dynamic so it could compensate ground effects during use. I had made good progress on Stage 1 but then left for FTP. I've toyed around with some ideas since then but nothing serious.

[Melbeta]

Hi Carl, I was looking through the Compass Challenger X70 and X80 models, and they used a Servo, the circuit was designed by John Earle back then, who was the Chief Engineer, who subsequently left Compass Electronics, went to Whites Electronics, and I think was Chief Engineer, where you worked. My question is this. What was a Servo, and what did Compass do with such Servo with the X70 and X80. That is if you know the answers. I know the X70 differed from X80 model, in that the X70 used an earlier GOOD/BAD meter, while the X80 used an new TID meter. I examined the MSC circuit (Meter Service Control), and determined the two MSC circuits were not the same, but were similar in design, with the MSC circuit for the TID meter much larger in design. Was the Servo connected to the meter circuits, or to the coil? Servo is just a word to me right now.
Melbeta

[EL NINO]

[QUOTE=Sean_Goddard;284515]Has anyone made a coil which "autobalances"?

I am under the impression that one of the biggest problems which affect sensitivity of a VLF is Rx saturation due to the mineral matrix in the ground setting up a "standing" signal thus masking the tiny target signals. I want to know if anyone has made a ground balance system which nulls the COIL to the effect of the mineral matrix thus (theoretically) increasing the amount of gain which can be used in the Rx thus giving better sensitivity?[/QUOTE

Sean ... it's a possible increase in Gain.it's not just theoretical ..

.you are on a good road

[Carl-NC]

Hi Carl, I was looking through the Compass Challenger X70 and X80 models, and they used a Servo, the circuit was designed by John Earle back then, who was the Chief Engineer, who subsequently left Compass Electronics, went to Whites Electronics, and I think was Chief Engineer, where you worked. My question is this. What was a Servo, and what did Compass do with such Servo with the X70 and X80. That is if you know the answers. I know the X70 differed from X80 model, in that the X70 used an earlier GOOD/BAD meter, while the X80 used an new TID meter. I examined the MSC circuit (Meter Service Control), and determined the two MSC circuits were not the same, but were similar in design, with the MSC circuit for the TID meter much larger in design. Was the Servo connected to the meter circuits, or to the coil? Servo is just a word to me right now.
Melbeta

I'd have to look at the schematic to see what he was doing, but I doubt it was a servo for nulling the coil.